Tissue samples from infants (< 3 years old) with histologically confirmed primary intracranial CNS medulloblastoma/PNET, atypical teratoid/rhabdoid tumor, or choroid plexus carcinoma and with no prior chemotherapy, radiotherapy, or treatment from any other investigational agent will be used for this research study. Patients who meet the eligibility criteria, are treated at a PBTC institution that has IRB approval of this study, and consent to the usage of stored tumor specimens for the study objectives constitute the study population.